Ihave an unlimited supply of standard 6-sided dice. what's the fewest number of dice that i have to simultaneously roll to be at least 90% likely to roll at least one 6?

Every weekday, mr. jones bikes from his home to his job. sometimes he rides along two roads, the long route that is shown by the solid lines. other times, he takes the shortcut shown by the dashed line. how many fewer kilometers does mr. jones bike when he takes the shortcut instead of the long route?